Circuit breaker



sept. s, 193e. .w A. ATWQOD 2,053,934

CIRCUIT BREAKER Filed July 2, 1935 VVYTF ield A. Atwood,

bld 77( H i5 Attor'ruelj.

Patented Sept. 8, 1936 UNITED vSTATES CIRCUIT BREAKER Winfield A.Atwood, Yeadon, Pa., assignor to General Electric Company, a corporationof New York Application July4 2, i935, Serial No. 29,479

6 Claims. (Cl. 200-116) My invention relates to multi-pole circuitbreakers, more particularly to multi-pole circuit breakers of thetrip-free type in which the circuit controlling contacts are manuallyoperable be- 5 tween open and closed circuit positions and areautomatically operable to the open circuit position upon the occurrenceof predetermined abnormal current conditions, yand has for an object theprovision of a simple, reliable and inexpensive l circuit breaker ofthis character.

As is well known, present manufacturing methods are so adapted to largequantity production that the manufacturing cost per item decreases asthe quantity of production increases. For oblo vious reasons the demandfor single-pole circuit breakers is considerably greater than the demandfor multi-pole circuit breakers, and consequently, the cost of thesingle-pole circuit breaker parts is comparatively low. In order todecrease the 20 cost of multi-pole circuit breakers, it has heretoforebeen proposed to construct such circuit breakers by using, insofar aspossible, the same parts as are used in constructing single-pole circuitbreakers. In all cases with which I am 25 familiar, however, resort hasbeen had to arrangements in which a single, rugged operating mechanismis arranged simultaneously to operate the contacts of the individualpoles by means of a common crossbar connected to the contacts of 30 eachpole, and the single, rugged mechanism is 'provided with tripping meansfor operating the crossbar to open the contacts upon the occurrence ofoverload conditions. Although such an arrangement has many advantageswhen applied to 35 large size circuit breakers, I have found itunsuitablefor small size circuit breakers of certain types.

In my copending application Ser. No. 667,855, filed April 25, 1933,entitled ,Circuit breakers and in the copending .application of LudwigS. Walle Ser. No. 667,856, led April 25, 1933, entitled Circuitbreakers, both of which applications are assigned to the same assigneeas the present invention, circuit breakers are disclosed which depend toa large extent on the self-generation of high gas pressures within asealed compression chamber for the successful interruption of currentsof short-circuit magnitude. In these circuit breakers, the contactsm'ove within the compression chamber, and the high gas pressures are ofcourse applied to the face of the movable contact and exert upon it anaccelerating force of great magnitude. Since the pressure developedwithin the compression chamber may be as high as 5000 lbs; per squareinch, it will be appreciated that the force exerted on the movablecontact will be of such magnitude as to drive the movable contact to theopen circuit position at a high l speed. In fact, as 'pointed out in myIabove referr'ed to application, it has been found advisrequirements.

able to provide a special type of frame for absorbing the blow incidentto the expulsion of the movable contact from the compression chamber bythe pressure generated therein.

If the above referred to arrangement for con- 5 structing multi-polecircuit breakers from singlepole circuit breaker parts is utilized toconstruct small size circuit breakers of the compression chamber type,i. e. to 100 amperes, the 'cost is prohibitive, due to the necessity ofspecially de- 10 signing the single operating mechanism to withstand theforces developed and to meet the space Furthermore, when the contactsare connected directly to a common crossbar, as described above, theforce exerted on the crossl5 bar, when the movable contact of one poleis expelled by the high pressures generated within the compressionchamber, will often twist the crossarm laterally to such a-n extent asto prevent the opening of the other poles of the circuit breaker.Accordingly, much is yet to be desired in small size multi-pole circuitbreakers of this type, and it ls a further object of my invention to Aprovide a multi-pole circuit vbreaker of .the compression chamber typewhich is constructed substantially entirely of single-pole circuitbreaker parts, which is economical to construct and whic is efficientand reliable in its operation.

In carrying out my invention in one form, I provide a multi-pole circuitbreaker, each pole of which comprises a single-pole circuit breaker unithaving a movable contact resiliently connected to an operating memberfor operation between open and closed circuit positions, the resilientconnection providing for operation of the Contact to its open circuitposition irrespective of the position of the operating member. Eachsingle-pole unit also includes a current-responsive element andtrippingmeans releasable to operate the movable contact to open circuitposition. In order to provide for simultaneous opening and closing ofall of the poles of the-circuit breaker,

I provide a rigid crossbar connected to the respective operating membersof the single-pole L units and a rigid crossbar connected to thetripping means of each unit, the last-mentioned crossbar being providedwith a latch which is operable by the current-responsive elements of oneor more of the single-pole units to release the crossbar whereby thetripping means connected thereto operate the contacts to the opencircuit position upon the occurrence of overload conditions.

For a more complete understanding of my invention, reference may now behad to the drawing in which Fig. 1 is a plan view of a three-polecircuit breaker embodying my invention, the cover of the circuit breakerhaving been removed to show the operating mechanism;' and Fig. 2 is asectional, elevational view taken along the line 2 2 of Fig. 1 certainparts being shown. in elevation more clearly to illustrate themechanism.

Referring now to the drawing, 1 have shown my invention in one form asapplied to a multipole circuit breaker i@ comprising a plurality ofsingle-pole circuit breaker units i i, i2 and i3 each of which isidentical in construction. As shown best in Fig. 2, each of thesingle-pole units of which only the unit i2 will be described, comprisesa base formed of insulating material, which base includes a housing itlformed integrally therewith for supporting a compression chamberinterrupter of the type described and claimed in the above-identifiedWalle application. This interrupter comprises a casing i5 formed ofsuitable pressure-resistant material such, for example, as brass and apair of insulating bushings i5 and i'i formed of kerosene-free fiber.Supported by the insulating bushing i l is a stationary contact i@connected by a conductor i9 to a terminal 25. Slidably journaled in thebushing i5 for movement between openl and closed circuit positions, is amovable contact 2i, the extending end of which is connected to thecircuit breaker operating mechanism.

As shown, the operating mechanism comprises a pair of overcenter springs22 and 23, the respective lower ends of which are connected to theopposite ends of a pin 2d which extends through a vertical slot (notshown) provided in the extending end of the movable contact 2 i. Theother ends of the overcenter springs are connected to a pin 25, theopposite ends of which are supported by a pair of levers 25. As shown,these levers are pivotally mounted on the opposite sides of a U-shapedframe 2l by meansof a pin 28, and the pin 25 extends through a slot 29formed in an operating member 3@ pivoted on a pin 3i supported by theframe 2l. In order to provide for reciprocal, longitudinal movement ofthe contact2i, a guide arm 32 is arranged with one end pivoted on thepin 3i and its opposite end connected to the pin 2d. Intermediate theends of the guide arm 32 is a crossportion 33 arranged in cooperatingrelation with one arm 3d of a bifurcatedtripping member which isnormally biased to an open circuit position by means of a compressionspring 35. As is more fully described in my above referred to copendingapplication, the compression spring 35 operates against 'a plunger rod36, one end of which engages a notch 3l formed in the tripping member.As shown, the, movable contact 2i is electrically connected by means ofa i'lexible conductor 38 to an L-shaped conductor 39 which is connectedto one leg of a substantially U-shaped thermal element L30, the otherleg of the thermal element being connected by means of an L-shapedconspective bases. A single cover 56 formed of insulating material isprovided which extends over the three units, and is provided with anaperture lll through which extends an insulated handle 158 which issecured to the operating member 30 of the single-pole unit i2.

In order to provide for simultaneous operation of the movable contacts2i of each of the singleaosaoae pole units, I provide a crossbar i9formed of insulating material which is secured to the operating membersSii of the respective units by suitable screws 50. Itwill be apparentnow that when the operating handle f3@ is moved in a left-handdirection, as viewed in the drawing, from its on position, shown, to itsE position, the operating member 3@ of the single-pole unit i 2 will berotated in a counterclockwise direction about the pivot pin 3i, and thiscounterclockwise direction will be transmitted by the crossbar to thecorresponding operating members oi the single-pole units ii and i3.Accordingly, the overcenter springs 22 and 25 of each unit will becarried. overcenter relative to the pins 3i, and the movable contacts 2iof each unit will be operated to the open circuit position with a snapaction. Similarly, the movable contacts 2i of each unit may be operatedto the closed circuit position by returning the handle 58 to .the onposition shown-in the drawing.

1t will be remembered that each unit includes a bifurcated trippingmember having an arm Bil which is biased to an open circuit position bya compression spring 35, and it l.will be apparent that in order toprovide for manual operation of the movable contacts between open andclosed circuit positions, means must be provided for ncrmally retainingthe tripping members in the position shown in the drawing against thebias of the compression springs 35. In certain types of single-polecircuitbreakers heretofore proposed, such, for example, as the circuitbreakers disclosed in my above-identied application, the tripping memberhas been provided with a latch arranged normally to engage a thermalelement corresponding to the thermal elementl so that when the thermalelement is heated upon the occurrence of an overload, the trippingmember is released for operation by the associated compression spring tomove the contacts to their open circuit position. While such anarrangement would be suitable for multi-pole circuit breakers embodyingmy invention where it is desired that each pole shall be opened uponoverload independently of the other poles of the circuit breaker, Iprefer to provide means for simultaneously operating the contacts ofeach unit tothe open circuit position upon the occurrence of an overloadin any one of the poles.

Accordingly, I have provided a crossbar l formed ofinsulating materialwhich extends across the three units i i, l2 and i3 and is secured tothe other arm Sila of the bifurcat'ed tripping,

member of each unit; Secured to the crossbar 5I centrally thereof, is alatch 52 arranged normally to engage a U-shaped pivoted latching member53 which is pivoted on a pin 56 supported at its opposite ends on aU-shaped frame 55. As shown, the latching member 53 is biased forrotation in a counterclockwise direction by a spring 56 and includes alatching portion 57, a, resetting portion 58 and a pair of extendingfingers 59, the extending fingers 59 being arranged normally to engagelatching extensions 59acarried by a T- shaped trip bar 50 to maintainthe latching member 53 in the position shown in the drawing. In orderthat the counterclockwise rotation of the latching member 53 under thebias of the spring 56 may be arrested in the proper position for thesubsequent resetting operation to be hereinafter described, a suitablestop pin 53a (Eig. 1) is provided extending inwardly from one leg of theU- shaped frame 55 into the path of movement of one 0I the fingers 59.The section line 2-2 is so located that the pin 53a would not ordinarilybe shown in Fig. 2. I have therefore shown in broken lines in Fig. 2 asmall circle which indicates the position of the pin 53a relative to thelatching member 53. The lower end of trip bar 6U is pivoted, as shown,on a pin 6I supported by the frame 55, and the trip bar is normallybiased to the position shown in the drawing by a torsion spring 62 whichsurounds the pin 6l.

As shown best in Fig. 1, the trip bar Bil extends across the threesingle-pole units I I, I2 and I3 and is provided with a plurality ofinsulating buttons 63 arranged to cooperate with the thermal ele-` lfreeend of the thermal element or elements to move in a left-hand directionas viewed in the drawing, and rotate the trip bar 60 in acounterclockwise direction about the pin 6I. As soon as the latchingextensions 59a on the trip bar 60 move out from under the left-hand endof the extending fingers 59, the latching member 53 will be rotated in acounterclockwise direction to a position in which one of the fingers 59engages the stop pin 53a by the spring 56 and by the force exerted onthe latching portion 51 by the latch 52 due to the force exerted by thecompression springs 35. Thereupon the latch 52 will be released and thetripping members of all of the .units will be rotated in a clockwisedirection about their pivots 3| so that the arms 34 will engage thecross members 33 and operate the movable contacts 2| to the open circuitposition.

In order to reclose the circuit breaker after it has been automaticallyoperated to the open cir- "cuit position, it is necessary iirstto movethe handle 48 from a mid-position which it will assume upon automatictripping of the circuit breaker to the on position. During this movementof the handle 4B, it will be apparent that a shoulder El on each of theoperating elements 3B will engage the arm 34a of the associated trippingmember to return it to its normal position and at the same time, thelatch 52 will engage the resetting portion 58 of the latching member 53so as to rotate it in a clockwise direction about its pivot 5t againstthe force of the spring 56 to the position shown in the drawing, thelatch 52 extending into the opening between the portions 5I and 58. Ifthe thermal elements 40 have cooled suiciently to permit the circuitbreaker to be reclosed, the trip bar 60 will be operated by the torsionspring 62 to its normal position so that the latching extensions 59awill engage the under sides of the extending ngers 59 on the latchingmember 53 to retain it in the position shown. The circuit breaker maynow be reclosed by moving the handle 48 to its on position, the trippingmembers of the units being retained in the position shown in the drawingby the engagement of the latch 52 with the latchin'g member 53. Y

I have found that under some conditions of operation, a short-circuitcurrent may ilow through one of the poles of. the circuit Abreaker ofsumcient magnitude to produce arcing between the contacts and aresultant generation of pressures of great magnitude. When this occurson one of the end poles of the circuit breaker, i. e., either the poleII or the pole I3, the force applied to the movable contact of that poleis suicient to operate it quickly to the open circuit position, theoperation of the other poles to the open circuit position occurring onlyafter the current responsive tripping mechanism has had time to operate.Since the movable contact of each of the singlepole units is biased toits closed position solely by the resilient means comprising theovercenter springs 22 and 23, the expulsion of the movable contact ofany one of the units from its compression chamber will have no eiect onthe remaining single-pole units'of the circuit breaker. If the movablecontacts had been directly connected together, however, for example, bymeans of a crossbar connected to the extending ends of the movablecontacts or to the cross member 33, expulsion of oneof the contacts dueto the generation of high pressures within one of the compressionchambers would exert a force on the crossbar which would tend totwist itlaterally to such an extent as to prevent the other poles -from opening.I am, of course, awane that it would be possible to make the crossbarand its mounting so rugged that the circuit breaker contacts could besecured directly together and operate as a unit without danger oftwisting the crossbar, but such a construction is inherently morevcostly, and I have found it to be of particular advantage to provideveach of the movable contacts with an individual resilient operatingmeans connected to the operating handle.

It will, of course, be understood that the particular form of operatingmechanism of each of the single-pole units forms no part of my presentinvention, and the mechanism shown should be taken simply asillustrative, since my invention is applicable generally to manydifferent types of operating mechanism. The particular operatingmechanism shown is of the type described and claimed in a copendingapplication of David C. Prince, Serial No. 7,085, filed February 18,1935, entitled Circuit breakers which application is assigned to thesame assignee as the present invention.

While I have shown a particular embodiment of my invention, it will beunderstood, of course, that I do not wish to be limited thereto sincemanymodifications may be made and I, therefore, contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of my invention.

What I claim as new and desireto secure by Letters Patent of therUnitedStates, is:

1. A multi-pole circuit breaker comprising a plurality of single-polecircuit breaker units each of which includes relatively movablecontacts, overcenter spring means for operating the contacts betweenlopen and closed circuit positions and overload means responsive to thecurrent flowing through said contacts, a crossbar extending across saidunits and operatively connected to each of the overcenter spring meansfor simultaneously operating the contacts of said units between saidopen and closed circuit positions, a second crossbar extending acrosssaid units, a latch normally retaining said last-mentioned crossbar in apredetermined position and releasable upon'operation of the overloadmeans of one or more of said units, each of said units including meansconnected to said last-mentioned a plurality of single-pole circuitbreaker units' crossbar for operating said contactsto open circuitposition upon release of said latch.

2. A multi-pole circuit breaker comprising a plurality of single-polecircuit breaker units each of which comprises a pair of relativelymovable contacts, an operating member, and resilient means connectedbetween said contacts and said member, a crossbar extending across saidunits and connected to the operating members thereof for simultaneouslyoperating the contacts of said units between open and closed circuitpositions, each of said units also including a tripping member normallybiased to operate saidcontacts to open circuit position against theforce exerted by said resilient means, a crossbar extending across saidunits connected to said tripping members, a latch for normally holdingsaid last-mentioned crossbar and said tripping members against thebiasing force thereon and current-responsive means for releasing saidlatch.

3. A multi-pole circuit breaker comprising a plurality oi single-polecircuit breaker units each of which comprises a pair of relativelymovable contacts, an operating member, and resilient means connectedbetween said contacts and said member, a crossbar extending across saidunits connected to the operating members thereof for simultaneouslyoperating said resilient means to move the contacts of said unitsbetween open and closed circuit positions, each of said'units alsoincluding a tripping member normally biased to operate said contacts toopen circuit position and an overload member movable in response to thecurrent through said contacts, a crossbar extending across said unitsconnected to the tripping members of said units, a latch for normallyholding said last-mentioned crossbar and said tripping members againstthe biasing force on said tripping members, and means operable by theoverload members of one or more of said units to release said latch.

4. YA multiple-pole circuit breaker comprising a plurality ofsingle-pole circuit breaker units each of which comprises a pair ofrelatively movable contacts, an operating member, and resilient meansconnected between said contacts and said member for operating saidcontacts'between open and closed circuit positions in response tooperation of said member while providing for movement of said contactsto open circuit position irrespective of the position of said member, acrossbar extending across said units and connected to the operatingmembers thereof for simultaneously operating the contacts between openand closed circuit positions, each of said units also including trippingmeans for operating the contacts of the unit to open circuit position, acrossbar extending across said units connected to said tripping means, alatch for normally retaining said last-mentioned crossbar and saidtripping means in a predetermined position, and current-responsive meansfor releasing said latch whereby the contacts of said units aresimultaneously operated to their open circuit positions by said trippingmeans upon the occurrence of predetermined current conditions.

5. In a multi-pole ,circuit breaker comprising each of which unitsincludes walls of pressureresistant material forming a substantiallygastight compression chamber, a pair of contacts mounted Within saidchamber one of which conabsence tacts extends through one of said wallsand is movable between open and closedcircuit positions, an operatingmember movable between on and oi positions, resilient means operable bysaid member for lmoving saidv one contact Vbetween said open and closedcircuit positions with a snap action, a tripping member for operatingsaid movable contact to said open circuit position independently of saidresilient means and overload means responsive to current ow through saidcontacts,` the volume of said compression chamber being such that underextreme short-circuit conditions gas pressures are generated therein ofsuch magnitude as to exert a force on said movable contact suiiicient toeiect a quick movement of said movable contact to said open circuitposition against the force of said resilient means, the combination ofmeans for rigidly securing said circuit breaker units together inside-by-side relation, a crossbar connected to the operating member ofeach of said units for simultaneously operating the movable contactsbetween said open and closed circuit positions while permittingindependent movement of any one of said movable contacts to said opencircuit position under said extreme short circuit conditions, a crossbarconnected to the tripping member of each of said units, a latch forholding said last-mentioned crossbar in a predetermined position andreleasable to eiect operation of said movable contacts to their opencircuit position, and means operable by the overload means of one ormore of said units for releasing said latch.

6. In a multi-pole circuit breaker comprising a. plurality ofsingle-pole circuit breaker units each of which includes contactsrelatively movable between open and closed circuit positions, anoperating member movable between on and off positions for causingmovement of said contacts between said open and closed circuitpositions, resilient means connected between one of said contacts andsaid member providing for movement of said contacts to open circuitposition irrespective of the position of said operating member, atripping member for operating said contacts to open circuit positionagainst the force exerted by said resilient means, overload meansresponsive to the current owing through said contacts and a sealedcompression chamber surrounding said contacts, the volume of saidchamber. being I' such that under extreme short-circuit conditions gaspressures are generated therein of such magnitude as to exert a force onsaid one contact suicient to eiect a quick movement of said one contactto said open circuit position against -,the force of said resilientmeans, thel combination of a crossbar connected to the operating memberof each of said units for simultaneously operating the contacts of saidunits between said open and closed circuit positions while permittinginde,- pendent movement of the contacts of any one of said units to saidopen circuit position under said extreme short-circuit conditions, acrossbar connected to the tripping members of each of said units andalatch operable by the overload means of one or more of said units forreleasing said last-mentioned crossbar and said tripping members wherebyinterruption of the current flow through each of said circuit breakerunits occurs at substantially the same time. i

WINFIELD n. A'rvvooD

